Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $214.80   7.636%   $231.2021   $231.20   $231.20   $231.20  
  Purchase #2 $179.95   13.755%   $204.7021   $204.70   $204.70   $204.70  
  Purchase #3 $189.89   11.428%   $211.5906   $211.59   $211.60   $211.60  
  Purchase #4 $58.30   3.438%   $60.3044   $60.30   $60.30   $60.30  
  Purchase #5 $68.75   5.728%   $72.688   $72.69   $72.70   $72.70  
  Purchase #6 $82.95   9.685%   $90.9837   $90.98   $91.00   $91.00  
  Purchase #7 $198.54   12.499%   $223.3555   $223.36   $223.35   $223.40  
  7 purchase totals = $993.18       $1,094.8264   $1,094.82   $1,094.85   $1,094.90